To provide access to the SSA tmssa device driver.
The Serial Storage Architecture (SSA) target-mode device driver provides an interface that allows the SSA interface to be used for data transfer from using system to using system.
You can access the data transfer functions through character special files that are named dev/tmssann.xx, where nn is the node number of the node with which you are communicating. The xx can be either im (initiator-mode interface), or tm (target-mode interface). The caller uses the initiator-mode to transmit data, and the target-mode interface to receive data.
The least significant bit of the minor device number indicates to the device driver which mode interface is selected by the caller. When the least significant bit of the minor device number is set to 1, the target-mode interface is selected. When the least significant bit is set to 0, the initiator-mode interface is selected. For example, tmssa1.im should be defined as an even-numbered minor device number to select the initiator-mode interface. tmssa1.tm should be defined as an odd-numbered minor device number to select the target-mode interface.
When the caller opens the initiator-mode special file, a logical path is set up. This path allows data to be transmitted. The user-mode caller issues a write, writev, writex, or writevx system call to start data transmission. The kernel-mode user issues an fp_write or fp_rwuio service call to start data transmission. The SSA target-mode device driver then builds a send command to describe the transfer, and the data is sent to the device. The transfer can be done as a blocking write operation or as a nonblocking write operation. When the write entry point returns, the calling program can access the transmit buffer.
When the caller opens the target-mode special file, a logical path is set up. This path allows data to be received. The user-mode caller issues a read, readv, readx, or readvx system call to start the receiving of data. The kernel-mode caller issues an fp_read or fp_rwuio service call to start the receiving of data. The SSA target-mode device driver then returns data that was received for the application program.